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Abstract

Background: Atrial fibrillation (AF) is a highly prevalent (30–50%) complication after cardiac surgery. Previous studies have reported that obesity is a risk factor for postoperative AF. However, it is unknown whether the metabolic syndrome (MS) is also a risk factor for AF. The objective of this study was thus to examine the effect of obesity and of MS on the occurrence of newonset AF after isolated coronary artery bypass grafting surgery(CABG).

Methods and results: We analyzed the incidence of postoperative AF in 5085 patients (mean age 64.4 ± .4 years; 77% of men) who underwent isolated CABG with no concomitant valvular surgery. Of these patients, 2320 (45.6%) had a MS as defined by the NCEP-ATPIII. AF was defined as any sustained episode during the postoperative hospital stay, requiring medical and/or electrical cardioversion. Overall, AF occurred in 1374 (27%) patients. Obesity was associated with higher (p=.0001) prevalence of AF: 35% in obese II (body mass index, BMI>5 kg/m2: n=67) patients versus 25% in normal weight (BMI≤n=386), 26% in overweight (25BMI≤30: n=257), and 29% in obese I (30<MI≤35: n=073) patients. This association was observed in the whole cohort as well as in patients older than 50 years (n=582; 90%). However, in patients ≤50 y/o (n=03; 10%), there was no relationship between incidence of AF and BMI. In these patients, MS was however associated with higher incidence of AF (12% vs. 6%; P=.01). On multivariate analysis, BMI>5 was an independent predictor (OR = 67; [CI: 1.28–2.12]; P=.0001) of postoperative AF in ≤50 y/o patients, whereas MS was not. To the opposite, in >0 y/o patients, MS was independently associated with the occurrence of AF (OR =.55; [CI: 1.2–5.5]; P =0.01), whereas BMI was not.

Conclusion: This study demonstrates that moderate-severe obesity (BMI>5) is a powerful risk factor for new-onset AF after isolated CABG in patients older than 50 years. However, this association is not observed in younger patients. In this young population, the MS is the only metabolic risk factor to be independently associated with AF. Studies examining prophylactic interventions in elderly patients with high BMI and in young patients with MS may be warranted.